Evolution of self-assembled Ge/Si(211) islands

Atomic force microscopy (AFM) and transmission electron microscopy have been used to investigate Ge islands, grown by molecular-beam epitaxy on Si(211) substrates with a nominal 15 Å Ge coverage at temperatures between 600 and 700 °C. The majority of islands grown at all three temperatures had irregular hexagonal footprints. Intermediate-sized islands grown at 650 and 700 °C became elongated laterally in the 〈111〉 direction parallel to the direction of substrate surface step edges. AFM cross-sectional analysis indicated that small coherent clusters were bound by 111 and 113 facets, whereas the largest dislocated clusters were primarily bound by 111 and 001 facets. The upper size bound for coherent clusters increased with increasing growth temperature.